JDBC的连接mysql与增删查改（二）

上一篇博客写到如何连接数据库和增删查改，但是每一次操作都需要写一个类，体现不到类的封装性，这篇博客讲详细介绍到如何封装类，并快速实现增删查改。

前提准备：

1.建包 
com.tao.entity 用于盛放实体类
com.tao.dao 用于接口的实现类
com.tao.test 用于测试类
2.建表
通过mysql，在school数据库下建立person表，
字段有id（int），name（varchar），pass（varchar），birthday（date）

BaseDao是一个基类，里面写好了一个连接数据库的方法connect（）和一个 关闭资源的方法closeAll（）；其他接口的实现类继承这个类，并调用他的方法即可。

BaseDao.java

package com.tao.dao;

import java.sql.Connection;
import java.sql.DriverManager;
import java.sql.PreparedStatement;
import java.sql.ResultSet;
import java.sql.Statement;

public class BaseDao {
	protected Connection conn = null;
	protected Statement stmt = null;
	protected ResultSet rs = null;
	protected String url = "jdbc:mysql://localhost:3306/school?characterEncoding=utf-8";
	protected String name = "root";
	protected String password = "root";
	protected PreparedStatement pstmt=null;
	
	public void connect(){
		try {
			Class.forName("com.mysql.jdbc.Driver");
			conn = DriverManager.getConnection(url, "root", "root");
			stmt = conn.createStatement();
		} catch(Exception e) {
			e.printStackTrace();
		}
	}
	
	public void closeAll(){
		try {
			if (rs != null) {
				rs.close();
			}
			if (stmt != null) {
				stmt.close();
			}
			if (conn != null) {
				conn.close();
			}
			if(pstmt!=null){
				pstmt.close();
			}
		}catch(Exception e) {
			
		}
	}
}

插入代码片

接下来，我们可以创建一个person类

Person.java

package com.tao.entity;

import java.util.Date;

public class Person {
	private int id;
	private String name;
	private String pass;
	private String birthday;

	public int getId() {
		return id;
	}

	public void setId(int id) {
		this.id = id;
	}

	public String getName() {
		return name;
	}

	public void setName(String name) {
		this.name = name;
	}

	public String getPass() {
		return pass;
	}

	public void setPass(String pass) {
		this.pass = pass;
	}

	public String getBirthday() {
		return birthday;
	}

	public void setBirthday(String birthday) {
		this.birthday = birthday;
	}

	@Override
	public String toString() {
		return "Person [id=" + id + ", name=" + name + ", pass=" + pass
				+ ", birthday=" + birthday + "]";
	}

	
	

}

然后写PersonDao类，这个类继承BaseDao，实现增删查改的方法

package com.tao.dao;

import com.tao.entity.Person;

public class PersonDao extends BaseDao {
	/*
	 * 登录
	 */
	public Person dologin(String name, String pass) {
		Person s = null;
		try {
			super.connect();
//			String sql = "select * from person where name='" + name
//					+ "' and pass='" + pass + "'";
//			rs = stmt.executeQuery(sql);
			String sql="select * from person where name=? and pass=?";
			pstmt=conn.prepareStatement(sql);
			pstmt.setString(1, name);
			pstmt.setString(2, pass);
			rs=pstmt.executeQuery();
			while (rs.next()) {
				s = new Person();
				s.setId(rs.getInt(1));
				s.setName(rs.getString(2));
				s.setPass(rs.getString(3));
				s.setBirthday(rs.getString(4));
			}

		} catch (Exception e) {
			// TODO: handle exception
		}
		return s;

	}
	/*
	 * 删除
	 */
	public int delete(int id){
		int row=0;
		try {
			super.connect();
			String sql="delete from person where id="+id;
			row=stmt.executeUpdate(sql);
		} catch (Exception e) {
			// TODO: handle exception
		}
		return row;
		
	}
	/*
	 * 插入
	 */
	public int insert(Person p){
		int row=0;
		try {
			super.connect();
	//		String sql="insert into person values("+p.getId()+",'"+p.getName()+"','"+p.getPass()+"','"+p.getBirthday()+"')";
	//		row=stmt.executeUpdate(sql);
			String sql="insert into person(name,pass,birthday) values(?,?,?)";
			pstmt=conn.prepareStatement(sql);
			pstmt.setString(1, p.getName());
			pstmt.setString(2, p.getPass());
			pstmt.setString(3, p.getBirthday());
			row=pstmt.executeUpdate();
			
		} catch (Exception e) {
			e.printStackTrace();
		}
		return row;
		
	}
	/*
	 * 查询一个人
	 */
	public Person get(int id) {
		Person s = null;
		try {
			super.connect();
			String sql = "select * from person where id="+id;
			rs = stmt.executeQuery(sql);
			while (rs.next()) {
				s = new Person();
				s.setId(rs.getInt(1));
				s.setName(rs.getString(2));
				s.setPass(rs.getString(3));
				s.setBirthday(rs.getString(4));
			}

		} catch (Exception e) {
			// TODO: handle exception
		}
		return s;

	}
	/*
	 * 修改
	 */
	public int update(Person p){
		int row=0;
		try {
			super.connect();
			String sql="update person set name='"+p.getName()+"',pass='"+p.getPass()+"', birthday='"+p.getBirthday()+"' where id="+p.getId();
			row=stmt.executeUpdate(sql);
		} catch (Exception e) {
			e.printStackTrace();
		}
		return row;
		
	}
	
}

最后写测试类，测试结果

TestP.java

package com.tao.test;

import com.tao.dao.PersonDao;
import com.tao.entity.Person;

public class TestP {

	public static void main(String[] args) {
		/*
		 * 登录测试
		 */
		PersonDao pdao = new PersonDao();
		Person p1 = pdao.dologin("jack", "1' or'1'='1");
		if (p1 == null) {
			System.out.println("登录失败");
		} else {
			System.out.println("登陆成功");
			System.out.println(p1);
		}
		/*
		 * 删除测试
		 */
		int row = pdao.delete(5);
		if (row > 0) {
			System.out.println("del success..");
		} else {
			System.out.println("del failed");
		}
		/*
		 * 插入测试
		 */
		/*Person p2 = new Person();
		p2.setName("xiaoliu");
		p2.setPass("xiaoliu");
		p2.setBirthday("2018-8-18");
		int r=pdao.insert(p2);
		if (r > 0) {
			System.out.println("insert success..");
		} else {
			System.out.println("insert failed");
		}*/
		
		/*
		 * 查询一个获取学生并修改姓名
		 * 
		 */
		Person p3 = new Person();
		p3 = pdao.get(3);
		p3.setName("tom1");
		int rr = pdao.update(p3);
		if (rr > 0) {
			System.out.println("update success..");
		} else {
			System.out.println("update failed");
		}

	}

}